A. Field of the Invention
The invention pertains to fluid distribution systems, and particularly distributors of the perforated-pipe variety.
B. Background of the Invention
It is well known that uniform fluid distribution is essential for efficient operation of chemical processing equipment such as contactors, reactors, mixers, burners, heat exchangers, extrusion dyes and textile-spinning chimneys. Optimum distribution involves a proper consideration to flow behavior in the distributor, flow conditions upstream of the distributor, and flow conditions downstream of the distributor. The simplest of prior art distributors is called the "Perforated-Pipe" distributor which, in it's simplest form, is a pipe with a series of perforations spaced equidistant along its length. In such a simple system, flow distribution is uniform where there is a proper balance between kinetic energy and momentum of force of the inlet stream, friction losses along the length of pipe and pressure drop across the outlet holes. When inlet-stream kinetic energy and momentum force predominate, increasing amounts of fluid will be discharged as the flow travels toward the closed end; and when friction losses along the pipe predominate, decreasing amounts of fluid will be discharged as the fluid travels toward the closed end. When an upstream disturbance, such as produced by a bend, is superimposed upon a predominate inlet-stream kinetic energy and momentum force, the flow from the outlet holes near the distributor inlet and near the closed end can be greater than in the middle.
In a perforated-pipe distributor, in order to keep the distribution of the fluid uniform within .+-.5%, the ratio of kinetic energy of the inlet stream to pressure drop across the outlet hole and friction loss in the pipe to pressure drop across the outlet hole should be equal to or less than one-tenth.
Ordinarily, in the case of perforated-pipes, an orifice coefficient of 0.6 to 0.63 is used. However, the orifice coefficient is a function of hole size relative to pipe diameter and wall thickness, flow rate through the hole, flow rate in the pipe across the hole and the like; and so the value of the orifice coefficient can vary considerably from the values ordinarily employed. Additional experimental data is usually needed to define the above function. If the component of the hole outlet velocity normal to the pipe wall is larger than the velocity along the pipe, the effect of the pipe velocity on the orifice coefficient is diminished.
Pressure change due to friction and momentum recovery over the length of the perforated-pipe distributor can in theory be shown to be ##EQU1## where .DELTA.h.sub.p =net loss in head between the inlet and closed end of the pipe, ft. of flowing fluid; f=Fanning friction factor, dimensionless; L=pipe length, ft.; D=pipe diameter, ft.; V.sub.i =average fluid velocity at inlet to pipe, ft./sec.; g.sub.c =dimensional constant, 32.17 (lb. mass) (ft.)/(lb. force) (sec..sup.2).
In addition to such well recognized engineering considerations, fluid distribution is affected by the positioning of fluid outlet orifices in the system. The present invention improves fluid distribution by an orifice positioning pattern which increases uniformity of fluid distribution, particularly when the fluid flow considerations discussed above are observed.
An object of the instant invention is to provide a distribution system meeting the above requirements and incorporating the above mentioned considerations all the while achieving a more efficient distribution system than that described in the prior art.